hot-stage

hot-stage (third-person singular simple present hot-stages, present participle hot-staging, simple past and past participle hot-staged)

1. (intransitive) To light the engine(s) of a rocket stage while still attached to the stage beneath it.

   The Proton's second stage avoids ullage issues by hot-staging, allowing the engines to ignite while still being pushed by the first stage, but this necessitates the use of a special open trusswork in the interstage area to prevent the superheated second-stage exhaust from blowing up the rocket.